Obdurate or stupid, that is the question

Trump went on Fox this morning, taking a break from his recent (vain) effort trying to fill the shoes of those who held the office before him, and reverted back to his childish, aggrieved whinging about how it was all the Democrat's fault. Ugh!

And he has pivoted from the "it'll all be better by Easter, an Easter miracle" nonsense he was peddling just two days ago. Why? Apparently the CDC people showed him some pictures of a hospital overrun with patients; that gives you measure of the man. You can explain as you would to normal person of moderate intelligence and he takes no notice. Statistics are go over his head. He has so little imagination that listening to a nuanced argument and seeing its implications appears quite beyond him.

It was a picture that tipped the balance; and the stark warning that he could be the president to preside of 2.2m deaths:¹.  And lets remember this was a man who said it was no worse than the flu, better even because people who got sick often had less severe symptoms. And yes, he did say that. We have a president who needs to be presented facts as you would to an 8th grader to get through to him. But at least for a while data and reason are prevailing. 

1. That's 2.15m more Americans than died in Vietnam, President Bone Spurs

Herd immunity

As it turns out my suggestion (Reversing Course) is not novel. One of my biologist colleges noted this is what they refer to as "herd immunity".  Leaving aside the economic arguments that poverty will kill as many people as the virus (which looks rather like the trolley problem but that's for another post), the calculus should turn on how many lives might be lost under a herd immunity strategy vs. a lock-down strategy. 

Reversing course

For several weeks we have been trying to slow the spread of covid-19. Since it can't be eliminated the only way forward was to slow its spread sufficiently that the heath care system would not be overwhelmed. Some argued that the economic toll of a country-wide lock-down, which appeared to have worked in arresting the spread of covid-19 in China, would be so severe as to cause as many deaths as the virus itself. That at least made the possibility of trading off lock-down against business as usual less about death vs financial well being as about how many deaths each route might cause.
But slowing down the spread, while not leading to large numbers of fatalities, would still leave those who are most vulnerable at some risk, albeit ever smaller and albeit without having to worry about being triaged out of an ICU bed.

Perhaps we have been going about this the wrong way. The best defense is a firewall of immune people. And since we have no way of artificially creating immunity (vaccination), the only sure way of developing the antibodies is to get sick. So we need everyone who is at low risk to get sick (and recover) as fast as possible, so that they form an insulating barrier between those who are contagious (an ever declining number) and those who are most vulnerable.

The risk, of course, is that some we thought were low risk turn out to need hospitalization and we could precipitate the crisis we are trying to avoid. But as we learn more, this might be not only the fastest and therefore economically prudent way out of the crisis, it might also be the safest for all of us.
   

A simple model of covid-19 contagion

In the first set of simulations, eight thousand nodes were connected at random in a single network. Density was fixed to give a degree of about 10.  Each time period, each node "interacted" with all its direct contacts. The incubation period was 14 days after which symptoms should have manifest, leading quarantine and preventing further infection by that node. After another 7 days, the node was flagged as recovered (no long counted as a case) and deemed to be immune.

In the figure below the proportion of sick individuals was plotted for 364 time periods for six different transmission probabilities ranging from 1% to 2% . Halving the transmission probability reduced the peak number of concurrently infected people from over 25% at day 75 to about 7.5% at day 147, a 70% reduction.

The second set of simulations held the transmission rate constant 1.4% and tested different network density from 0.1% ( degree ~ 10 ), to 0.2% ( degree ~ 20 ).

What appears rather striking in comparing these two figures is how much more effective reducing transmission probability is that reducing network degree.

It may be that the social distancing strategy, reducing contact with network ties and in effect making the network significantly more sparse, is less effective than finding ways to reduce the probability of transmission at each interaction.
 



 

Missing the point

The second round of democratic presidential primary debates wrapped up last night, to be immediately followed by endless discussions about who one, who lost, who landed punches, who looked off balance. The format lends itself to sound bites and to some extent lets the interviewers of the hook by letting the contestants frame the issues. That drives scripted attacks in search of sound bites, trivializes the issues and highlights the divisions within the party.

None of the post debate analysis dug into the details of the policies being floated, so how is the viewer or reader to easily assess the merits of one vs another? What is missing is serious analysis of the kind Stephen Sackur practices so well.  (And that's what makes the Beeb such a treasure)

Exponential growth, limited scalability

Saying that the spread of covid-19 is "exponential" is vague; what matters is the size of the exponent. Without testing, without "social distancing", its spread is unabated and the exponent is large. Measures to slow its spread will lower the value of the exponent; in other words, "flattening the curve".

The curve here is steeper than with other viruses because it is thought to be transmissible before people get sick. Usually when people get sick they stay home to recover and so are far less likely to pass it on to others; with covid-19, when someone gets sick they may will have passed it on to tens of other who in turn have passed it on to hundreds and so on.  That's what makes this contagion so problematic.

The goal of eliminating the virus is, in all likelihood, no longer attainable. Too many people have been infected to make containment an option. It is therefore important to understand what mitigation means. The most critical issue is the capacity to treat those who are in the high risk category, generally thought to be those with preexisting respiratory ailments.

Since there is no known cure most will require elaborate medical care, often in an Intensive Care Unit (ICU). ICUs are not something that can be created in short order, they are not easily salable because they require not only equipment that can't be manufactured fast enough but, more importantly, trained staff to operate them who can't be trained or recruited in time.

If the rate of new infractions among the vulnerable leads to a situation (as it did in Italy) where the number needing access to an ICU at a point in time exceeds their availability, people will die unnecessarily.  That has to be prevented.

Since ICUs can't be created fast enough, the only option is to slow the rate of arrival of new cases so that at its the peak, the number of simultaneously sick people who need access to an ICU is less than the number of ICU beds available. In other words, socially responsible actions that help flatten the curve will end up saving other people's lives.

Blaming Trump for covid-19

Trump's defenders have argued that he is not to blame for the Covid-19 pandemic. They are right that the disease initially spread from China, though others have pointed out that had he not dismantled the CDC's pandemic response unit, we might not have been where we are today. Whether his tweeting, bombast and false statements affected its spread is hard to say. But he may have been more instrumental in its spread than even he could have imagined.

His interaction with people at CPAC, one of whom was diagnosed with Covid-19, many have exposed him to the virus and he may have become a carrier, infecting those with whom he interacted. Doug Collin's "Self-quarantine" suggests this may be more than a random conspiracy theory.  How ironic, then, that the self proclaimed savior from the Corona virus in fact may have been an agent its spread!

An infectious grin

Trump, smiling, sat with experts in the West Wing and said he's doing the best job any president in history ever did at preventing a covid-19 epidemic. He encouraged people to go to work since few of them would be really sick. He told us that the experts had overestimated the fatality rate.

It would be comic were it not so tragic. His motives in ignoring expert advice to make assertions based on his own flawed hunches are unclear. It may be that he wants to prevent a panic; perhaps he wants to stop the slide in the stock market; perhaps we wants to ensure that GDP remains on track. Or it could be another example of Dunning-Kruger.  Whatever the explanation, he clearly has little interest in at-risk individuals' health, nor an understanding of the mechanisms of the viruses' spread.

It is notable that individual deaths allegedly at the hands of immigrants are splashed across Fox as a BIG DEAL, yet the casual causing of hundreds, if not thousands of deaths, by misleading people about covid-19, in his and Fox's view, is just a case of it can't be helped; 'shit happens'. There should be a private corner in Hell for Trump, the GOP and Fox.